Such a device is known from Patent DE-3 438 756 as a D-STN (Double-Layer Super-Twisted Nematic) cell or double-layer twisted nematic cell. In that case the display device is put together out of two nematic liquid-crystal cells that are arranged at a distance one behind the other, one of which cells serves to provide information and the other as a compensating cell for increasing the contrast.
However, the invention also extends to display devices that operate with other electro-optical effects; the concept of "cell" as used in this invention may also comprise a simple disc, for instance a filter disc or protective disc, which is to be supported at a distance for the purpose of preventing optical disturbances caused by Newton rings.
What is decisive is that the invention solves the technical problem of providing a clearance distance which is defined and, as a rule, as thin as possible (less than 1 millimeter), without significantly increasing the number of components to be assembled or excessively impairing the assembly process.
This task is solved by the construction described herein. For appropriate further developments, express reference is also made to the claims and to the descriptive drawings.
According to that solution, the supports--which in any case are required for the first-to-be-mounted cell--simultaneously serve (in conjunction with the thin angled legs that are designed onto the supports for that purpose) as spacers, in order to maintain the gap from the cell which will then be arranged in front of the first-mounted cell. Because of the construction of the display-device housing (e.g., in the course of connecting a viewside aperture frame with a rear light box), the two cells--supported one in front of the other--are then pressed on both sides against the spacer legs that protrude into the gap; the process may be further elastically enhanced by means of small springs designed to compensate for tolerances.
In any event, the above obviates the need for the prior expensive practice of inserting a separate thin frame-shaped circumferential spacer, taking the form of a cut-out built-in film or a pressure mass, made of adhesive or colorant and thickly applied to one of the surfaces, between the cells that are to be distanced from each other. What is more, there now remain sufficient openings--between the individual spacer-legs arranged at a distance next to each other, and next to the springs--for an exchange of air with the environment; this effectively counteracts any disturbances caused by the formation of spots due to the accumulation of moisture within the gap.